Various different wireless communication devices are well known and form a large part of our everyday lives. Examples of the well-known wireless communication devices include walkie-talkies and other simple two-way radios, cellular phones, pagers, and Palm-type handheld devices that permit e-mail or Internet access. Simple two-way radios require no network infrastructure, since each radio communicates directly with each other radio. However, simple two-way radios also offer none of the network-based features people expect of a modern communications system, such as the ability to set up a private connection between two communications devices using an identifier such as a phone number or name. Each of the other examples given of wireless communications devices requires an expensive network infrastructure to operate correctly.
One area where wireless communication devices can play an important role is in the workplace, to allow mobile employees to communicate with one another. Many workplaces have already installed a wireless computer network to support wireless devices such as laptop computers. These wireless computer networks use a standard wireless networking protocol, such as one of the 802.11 standards, and consist of one or more wireless access points, typically installed in the ceiling of a building. The access points communicate with various wireless devices using the selected standard wireless networking protocol, and communicate with each other, and with other computers, over a standard wired computer network, such as Ethernet. Since a full-featured modern communication system requires a network infrastructure to operate correctly, it makes sense to develop a wireless communications system, which uses a typical wireless computer network (such as one based on an 802.11 standard) as its network infrastructure. This makes it possible to deploy a wireless communications system without the need to deploy a completely separate parallel wireless network.
An important feature of communications systems in general, and wireless communications systems in particular, is the ability to interpret user utterances and to perform appropriate actions based upon those utterances, a capability which will be referred to as “speech recognition.” Speech recognition is most important when a wireless communications system employs miniature communication devices that are too small to provide a keypad or directory. In such a system, speech recognition becomes more of a necessity than a convenience, because voice commands provide the primary means of controlling the wireless devices.
Various different speech recognition systems are well known and form a large part of our everyday lives. Examples of the well known speech recognition systems include systems for determining airline flight information, systems for accessing billing information, systems for providing directory assistance, systems for allowing service activation, and systems for navigating through a branching tree of possible choices in a customer contact center. Each of these systems processes an utterance by matching it with a single interpretation in the set of all possible interpretations. The set of all possible interpretations of an utterance will be referred to as the “recognition space.” Note that the recognition space in a speech recognition system is always finite.
All speech recognition systems require an accurate interpretation of an utterance to perform an appropriate action; however, speech recognition systems are not foolproof and use probabilities to determine the likeliness of each possible utterance interpretation. A number of factors affect speech recognition accuracy, including the phonetic distinctiveness of items in the recognition space, the ability of system users to dynamically change the recognition space, the accent of a person issuing an utterance, simple mispronunciations, and so on. Each of these factors is greatly affected by the size of the recognition space. A large recognition space increases the likelihood of confusability and causes all of the factors that impact speech recognition to become severe problems.
One example of a potentially very large recognition space is a directory of user names, which can exist when a communications system has a large number of users who rely on voice commands to contact each other. This problem grows as the communications system itself grows, effectively providing a limit to the continued success of the system. All communications systems, such as telephones or fax machines, become more useful as more people employ them. When a communications system with a spoken user directory acquires a large number of users, however, the size of the directory itself limits the effectiveness of the system, because it significantly reduces the accuracy of speech recognition.
A speech recognition system would realize a significant benefit by being able to find accurate interpretations of utterances in a large recognition space, especially when one or more of the following situations occur: entries in the recognition space change dynamically, the recognition space contains entries that are not phonetically distinctive, entries in the recognition space are easily mispronounced, and/or users of the system speak with accents. It is in light of this wireless communication and speech recognition background that the significant improvements of the present invention have evolved.